usr.bin/telnet/ring.c

   1 /*
   2  * Copyright (c) 1988, 1993
   3  *      The Regents of the University of California.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the University nor the names of its contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  *
  29  * @(#)ring.c   8.2 (Berkeley) 5/30/95
  30  * $FreeBSD: src/crypto/telnet/telnet/ring.c,v 1.2.8.2 2002/04/13 10:59:08 markm Exp $
  31  */
  32
  33 /*
  34  * This defines a structure for a ring buffer.
  35  *
  36  * The circular buffer has two parts:
  37  *(((
  38  *      full:   [consume, supply)
  39  *      empty:  [supply, consume)
  40  *]]]
  41  *
  42  */
  43
  44 #include        <errno.h>
  45 #include        <stdio.h>
  46 #include        <string.h>
  47
  48 #ifdef  size_t
  49 #undef  size_t
  50 #endif
  51
  52 #include        <sys/types.h>
  53 #ifndef FILIO_H
  54 #include        <sys/ioctl.h>
  55 #endif
  56 #include        <sys/socket.h>
  57
  58 #include        "ring.h"
  59 #include        "general.h"
  60
  61 /* Internal macros */
  62
  63 #if     !defined(MIN)
  64 #define MIN(a,b)        (((a)<(b))? (a):(b))
  65 #endif  /* !defined(MIN) */
  66
  67 #define ring_subtract(d,a,b)    (((a)-(b) >= 0)? \
  68                                         (a)-(b): (((a)-(b))+(d)->size))
  69
  70 #define ring_increment(d,a,c)   (((a)+(c) < (d)->top)? \
  71                                         (a)+(c) : (((a)+(c))-(d)->size))
  72
  73 #define ring_decrement(d,a,c)   (((a)-(c) >= (d)->bottom)? \
  74                                         (a)-(c) : (((a)-(c))-(d)->size))
  75
  76
  77 /*
  78  * The following is a clock, used to determine full, empty, etc.
  79  *
  80  * There is some trickiness here.  Since the ring buffers are initialized
  81  * to ZERO on allocation, we need to make sure, when interpreting the
  82  * clock, that when the times are EQUAL, then the buffer is FULL.
  83  */
  84 static u_long ring_clock = 0;
  85
  86
  87 #define ring_empty(d) (((d)->consume == (d)->supply) && \
  88                                 ((d)->consumetime >= (d)->supplytime))
  89 #define ring_full(d) (((d)->supply == (d)->consume) && \
  90                                 ((d)->supplytime > (d)->consumetime))
  91
  92 /* Buffer state transition routines */
  93
  94 int
  95 ring_init(Ring *ring, unsigned char *buffer, int count)
  96 {
  97     memset((char *)ring, 0, sizeof *ring);
  98
  99     ring->size = count;
 100
 101     ring->supply = ring->consume = ring->bottom = buffer;
 102
 103     ring->top = ring->bottom+ring->size;
 104
 105 #ifdef  ENCRYPTION
 106     ring->clearto = 0;
 107 #endif  /* ENCRYPTION */
 108
 109     return 1;
 110 }
 111
 112 /* Mark routines */
 113
 114 /*
 115  * Mark the most recently supplied byte.
 116  */
 117
 118 void
 119 ring_mark(Ring *ring)
 120 {
 121     ring->mark = ring_decrement(ring, ring->supply, 1);
 122 }
 123
 124 /*
 125  * Is the ring pointing to the mark?
 126  */
 127
 128 int
 129 ring_at_mark(Ring *ring)
 130 {
 131     if (ring->mark == ring->consume) {
 132         return 1;
 133     } else {
 134         return 0;
 135     }
 136 }
 137
 138 /*
 139  * Clear any mark set on the ring.
 140  */
 141
 142 void
 143 ring_clear_mark(Ring *ring)
 144 {
 145     ring->mark = 0;
 146 }
 147
 148 /*
 149  * Add characters from current segment to ring buffer.
 150  */
 151 void
 152 ring_supplied(Ring *ring, int count)
 153 {
 154     ring->supply = ring_increment(ring, ring->supply, count);
 155     ring->supplytime = ++ring_clock;
 156 }
 157
 158 /*
 159  * We have just consumed "c" bytes.
 160  */
 161 void
 162 ring_consumed(Ring *ring, int count)
 163 {
 164     if (count == 0)     /* don't update anything */
 165         return;
 166
 167     if (ring->mark &&
 168                 (ring_subtract(ring, ring->mark, ring->consume) < count)) {
 169         ring->mark = 0;
 170     }
 171 #ifdef  ENCRYPTION
 172     if (ring->consume < ring->clearto &&
 173                 ring->clearto <= ring->consume + count)
 174         ring->clearto = 0;
 175     else if (ring->consume + count > ring->top &&
 176                 ring->bottom <= ring->clearto &&
 177                 ring->bottom + ((ring->consume + count) - ring->top))
 178         ring->clearto = 0;
 179 #endif  /* ENCRYPTION */
 180     ring->consume = ring_increment(ring, ring->consume, count);
 181     ring->consumetime = ++ring_clock;
 182     /*
 183      * Try to encourage "ring_empty_consecutive()" to be large.
 184      */
 185     if (ring_empty(ring)) {
 186         ring->consume = ring->supply = ring->bottom;
 187     }
 188 }
 189
 190
 191
 192 /* Buffer state query routines */
 193
 194
 195 /* Number of bytes that may be supplied */
 196 int
 197 ring_empty_count(Ring *ring)
 198 {
 199     if (ring_empty(ring)) {     /* if empty */
 200             return ring->size;
 201     } else {
 202         return ring_subtract(ring, ring->consume, ring->supply);
 203     }
 204 }
 205
 206 /* number of CONSECUTIVE bytes that may be supplied */
 207 int
 208 ring_empty_consecutive(Ring *ring)
 209 {
 210     if ((ring->consume < ring->supply) || ring_empty(ring)) {
 211                             /*
 212                              * if consume is "below" supply, or empty, then
 213                              * return distance to the top
 214                              */
 215         return ring_subtract(ring, ring->top, ring->supply);
 216     } else {
 217                                     /*
 218                                      * else, return what we may.
 219                                      */
 220         return ring_subtract(ring, ring->consume, ring->supply);
 221     }
 222 }
 223
 224 /* Return the number of bytes that are available for consuming
 225  * (but don't give more than enough to get to cross over set mark)
 226  */
 227
 228 int
 229 ring_full_count(Ring *ring)
 230 {
 231     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 232         if (ring_full(ring)) {
 233             return ring->size;  /* nothing consumed, but full */
 234         } else {
 235             return ring_subtract(ring, ring->supply, ring->consume);
 236         }
 237     } else {
 238         return ring_subtract(ring, ring->mark, ring->consume);
 239     }
 240 }
 241
 242 /*
 243  * Return the number of CONSECUTIVE bytes available for consuming.
 244  * However, don't return more than enough to cross over set mark.
 245  */
 246 int
 247 ring_full_consecutive(Ring *ring)
 248 {
 249     if ((ring->mark == 0) || (ring->mark == ring->consume)) {
 250         if ((ring->supply < ring->consume) || ring_full(ring)) {
 251             return ring_subtract(ring, ring->top, ring->consume);
 252         } else {
 253             return ring_subtract(ring, ring->supply, ring->consume);
 254         }
 255     } else {
 256         if (ring->mark < ring->consume) {
 257             return ring_subtract(ring, ring->top, ring->consume);
 258         } else {        /* Else, distance to mark */
 259             return ring_subtract(ring, ring->mark, ring->consume);
 260         }
 261     }
 262 }
 263
 264 /*
 265  * Move data into the "supply" portion of of the ring buffer.
 266  */
 267 void
 268 ring_supply_data(Ring *ring, unsigned char *buffer, int count)
 269 {
 270     int i;
 271
 272     while (count) {
 273         i = MIN(count, ring_empty_consecutive(ring));
 274         memcpy(ring->supply, buffer, i);
 275         ring_supplied(ring, i);
 276         count -= i;
 277         buffer += i;
 278     }
 279 }
 280
 281 #ifdef  ENCRYPTION
 282 void
 283 ring_encrypt(Ring *ring, void (*encryptor)(unsigned char *, int))
 284 {
 285     unsigned char *s, *c;
 286
 287     if (ring_empty(ring) || ring->clearto == ring->supply)
 288         return;
 289
 290     if (!(c = ring->clearto))
 291         c = ring->consume;
 292
 293     s = ring->supply;
 294
 295     if (s <= c) {
 296         (*encryptor)(c, ring->top - c);
 297         (*encryptor)(ring->bottom, s - ring->bottom);
 298     } else
 299         (*encryptor)(c, s - c);
 300
 301     ring->clearto = ring->supply;
 302 }
 303
 304 void
 305 ring_clearto(Ring *ring)
 306 {
 307     if (!ring_empty(ring))
 308         ring->clearto = ring->supply;
 309     else
 310         ring->clearto = 0;
 311 }
 312 #endif  /* ENCRYPTION */